The "top" is not from a Boss 351, has Motorcraft cast on, top should not have lettering. I think your carb has an electric choke, also not Boss 351. The small hooks on the two Zs don't seem right, going from a very old memory. The top also uses the large thread filter, the Boss 351 used the small filter thread. It could be someone changed the top and the choke, or the whole carb could be bogus. Chuck